This invention relates generally to improvements in clutch-brake mechanisms; and has specific application to load hoisting or pulling, or so-called "come-along" lever-operated "ratchet hoists" or "pullers". Such devices are manually operated for raising and lowering loads, tensioning wires or cables, and the like; and are disclosed for example in U.S. Pat. Nos. 2,608,107 and 2,243,361. Such tools are so constructed that whenever the load is not being taken directly by the manually operated lever, the load is sustained independently of the operating lever by reason of automatic operation of friction clutch-brake means incorporated within the mechanism. However, the invention is similarly applicable to motor driven hoists or the like.
Such mechanisms are typically called upon to operate in dusty, dirty, wet and/or muddy environments. By way of example, they are dropped upon and dragged across coal mine floors; building construction sites; and the like. Such exposures contribute to early deterioration and reduced life of the friction pad and metal plate portions of such mechanisms.
The primary object of the present invention is to provide an improved clutch-brake friction pad/plate construction, whereby the mechanism per se substantially prevents ingress of abrasive materials from externally thereof, and at the same time provides throughout its operational life maximum mechanical advantage for its operational purposes. Incident thereto, the invention improves the wearing life of the mechanism. These objects are accomplished by novelly shaping (with respect to their sectional configurations) the frictionally engaging members of the unit, whereby the system is kept clear of contaminants from externally thereof such as would otherwise foul the relatively moving friction supplying parts. In consequence, the mechanism performs at all times at optimum mechanical advantage, and is continuously reliable and is of longer wearing operational life.
Prior arrangements known to applicant which are designed to exclude entrance of external dirt, etc. into such mechanisms are disclosed in U.S. Pat. Nos. 1,684,185; 2,739,789; 3,056,480 and 4,156,521.
As distinguished from the above, the co-acting friction supply surfaces of the present invention are uniquely (sectionally) shaped, and are so arranged relative to the clutch-brake disc members as to prevent entrance of foreign materials from externally thereof into relatively moving parts of the mechanism when the clutch/brake mechanism is inoperative. Supplementary spring pressure supply means is also preferably provided in order to augment the external contaminant sealing operation as explained hereinabove. Hence, a more efficient and longer wearing, yet overall compact mechanism is provided.